The present invention relates to a radial vane swirl generator, and more particularly to rotatable radial vanes of a swirl generator.
A burner is one of the most important parts in the combustion system. The capability of the burner not only has great influence on the combustion efficiency but also closely relates to the stability of the flame, the effective application of the fuel and the discharge of pollutant.
Improper combustion technology and improper selection of burners not only influences the effective use of energy, but also results in air pollution due to emitting large amount of hazardous material by combustion.
Conventional burner applies a fan or a compressor to send the air into the combustion chamber to mix with the fuel for burning. The blades of such conventional burner are of fixed radial type. The practicians often apply low-excess-air combustion technics to industrial boiler. Moreover, by means of fuel gas recirculation, the peak temperature of flame can be reduced to control thermal-NO. Swirling flow generated by properly-designed swirl generator and fuel-gas recirculation can control the residence time of combustion gas and flame temperature so that controlling fuel-rich combustion, reducing peak temperature of flame, controlling residence time of combustion gas and partial fuel-rich combustion and increasing stability of flame are several important keys of advanced burner design.
When air flows through the fixed radial flow-guiding vanes to form swirling flow, if the pressure drop and turbulent intensity are too high, then the capability of the burner will be poor, and the flow-guiding vanes are fixed so that the swirl intensity thereof is fixed and can not be adjusted in accordance with combustion state to achieve a best combustion condition.
Therefore, a good swirl generator must have changeable swirl flow so as to achieve low pressure drop, low turbulent intensity and be capable of producing desired recirculation intensity and controlling partial fuel-rich combustion, lowering peak temperature, controlling residence time of combustion gas and increasing flame stability.
The swirler of this invention can produce swirling flow to change the speed of air flow and deflect the radial incoming flow to produce a divisional angular vector. The swirling air flow then passes through expansion quarrel to form the recirculation.
Generally, there are three manners of generating swirling flow field:
1. manner of tangential entry; PA1 2. manner of guided vanes; and PA1 3. manner of rotating pipe.
In this invention, radial vanes are used to produce required swirling flow field.
When the swirling flow passing through combustion chamber, bluff body and expansion chamber, the swirling air flow will create reverse pressure gradient to form a recirculation zone. Not only is fuel vigorously mixed with air around this recirculation zone, but also a portion of the hot combustion product gas is recirculated back to sustain proper ignition, thereby assuring flame stability.
Swirling flow has the good quality of increasing flame stability. The proper swirling flow generated by properly-designed swirl generator can control flame, maintain fuel-rich combustion, reduce peak temperature of flame, control residence time of combustion gas, inhibit creation of pollutant.
The radial vanes of this invention is designed to achieve swirl level under the lowest pressure drop and the lowest turbulent intensity. The rotatable radial vanes of this invention are capable of decreasing the pressure drop and turbulent intensity. The proper rotary angle of the radial vanes is within a 0-80 range to give a tangential momentum to radially guided flow and the swirl intensity can be changed following the rotary angle of the vanes to achieve a circulation zone for enhancing the stability of the flame.